WHEELCHAIR BACKREST

Abstract: The invention provides a backrest (20) having pairs of first and second couplings (28, 30, 32, 34) for attaching the backrest to a pair of spaced apart uprights on a wheelchair behing the seat. The backrest is suspended from the first couplings and is located longitudinally by the second couplings which simply engage the uprights and do not require parts to be added to the uprights. The invention also provides a backrest including a tilt mechanism (56, 80, 84) operable to tilt the backrest about the second couplings while reacting with the first couplings to change the location of the backrest relative to the first couplings. Adjustable side supports (150, 152) are also provided.

Description: DESCRIPTION WHEELCHAIR BACKREST TECHNICAL FIELD This invention relates to wheelchairs and more particularly to a backrest for use in a wheelchair to be supported by attachment to a pair of uprights forming part of the wheelchair structure and located behind the seat. The invention is of particular use with wheelchairs which collapse by bringing the sides of the wheelchairs together. BACKGROUND ART Wheelchairs fall under two distinct categories. Firstly those that are intended to remain in a fixed configuration, and secondly those that are intended to be collapsed for ease of transportation. Both types tend to use a pair of uprights behind the seat and a backrest is attached between these uprights. In the case of fixed wheelchairs, the backrest is not normally removed unless it requires maintenance, but in the case of collapsible wheelchairs, the backrest must be removed before the wheelchair can be collapsed. The present invention is of particular use with collapsible wheelchairs and is intended primarily for that purpose although it can be used wherever a backrest is supported between a pair of parallel uprights. Accordingly, the backrest will be described in use with a collapsible wheelchair although it will be appreciated from the foregoing comments that its use is not limited to such a structure. Removable backrests require a number of design parameters to be met. Primarily, they should be light, compact, and contain as much of the adjustment and attachment mechanism as possible so that only essential parts are exposed. The mechanisms used for attachment and release must be simple, robust, foolproof, and capable of attachment to the upright without structure which would interfere with folding the collapsible wheelchair. Further, the attachment mechanism must be such that no matter whether the backrest is attached properly or not, it can not be dislodged rearwardly out of the wheelchair by accidental misuse. The present invention has resulted from addressing these design parameters. DISCLOSURE OF THE INVENTION In one of its aspects the invention provides a backrest for use on a wheelchair having a pair of spaced uprights (24, 26) behind the seat, the backrest comprising: a main body shaped to support a user's back and having generally vertical sides; a pair of first couplings attached one to each side of the main body and including a pair of hangers attachable one to each of the uprights at substantially the same heights on the uprights, the couplings further including projections attached to the main body and engageable on respective ones of the hangers in front of the associated uprights to thereby support the backrest vertically and to prevent rearward movement of the backrest as the user leans on the backrest; and a pair of second couplings spaced vertically from the first couplings and one to each side of the main body and extending outwardly away from one another, each of the second couplings including a fixed forward locating element for engagement against the front of one of the uprights to also prevent rearward movement of the backrest as the user leans on the backrest, and a bolt for releasably engaging the rear of the upright to prevent forward movement until released to permit removal of the backrest from the wheelchair. In another of its aspects the invention provides a backrest for use on a wheelchair having a pair of spaced uprights behind the seat, the backrest comprising: a main body shaped to support a user's back and having generally vertical sides; a pair of first couplings attached to the main body and including a pair of aligned projections extending about a common axis, one to each of the vertical sides of the main body, and a pair of hangers for attachment to the uprights to support the backrest; a pair of second couplings spaced vertically from the first coupling and engageable with the uprights to locate the backrest to prevent movement forwardly or rearwardly; and a tilt mechanism coupled to the main body and to the projections and operable to move the projections relative to the main body to thereby tilt the main body about the second couplings and relative to the uprights. In yet another of its aspects the invention provides a backrest for use on a collapsible wheelchair of the type having a pair of uprights behind the seat, the backrest comprising: a main body; a pair of upper couplings including hangers for attachment one to each of the posts, structure attached to the main body for resting on the hangers, and keeper means coupled to the hangers and operable to lock said structure to the hangers; and lower couplings attached to the main body and releasably engageable loosely about the uprights to further locate the backrest on the uprights. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view of a backrest according to a preferred embodiment of the invention and shown installed on the rear uprights of a collapsible wheelchair; Fig. 2 is a perspective view taken generally from the front of the backrest in the position shown in Fig. 1; Fig. 3 is a perspective view generally from the rear of the backrest removed from the wheelchair; Fig. 4 is a top view in section on line 4-4 of Fig. 3 drawn to a larger scale and illustrating part of a lower coupling used to locate the backrest in the wheelchair; Fig. 5 is an isometric view of a part of an upper coupling used to suspend the backrest on the wheelchair and drawn to a scale larger than that used for Fig. 3; Fig. 6 is a sectional view on line 6-6 of Fig. 4; Fig. 7 is a side view of a lower part of the backrest (also to a larger scale) installed on the wheelchair and including a portion in section to better illustrate a tilt adjusting mechanism; Fig. 8 is a view similar to Fig. 7 and showing the tilt adjusting mechanism in a different position; Fig. 9 is a front view of the backrest simplified to illustrate an adjustable side support forming part of the backrest; Fig. 10 is a top section view on line 10-10 of Fig. 9 (drawn to a larger scale) and illustrating the side support in a fully forward position; and Fig. 11 (drawn adjacent Fig. 4) is a view similar to Fig. 10 and showing the side support fully withdrawn. BEST MODE FOR CARRYING OUT THE INVENTION Reference is made firstly to Fig. 1 which illustrates a backrest designated generally by the numeral 20 installed on a conventional collapsible wheelchair 22 having a pair of spaced apart parallel uprights 24, 26 to which the backrest is releasably attached. This is achieved by use of a pair of upper couplings 28, 30 which provide support in a vertical direction as well as locating the backrest relative to the uprights 24, 26. At the bottom of the backrest, a pair of lower couplings 32, 34 are used to provide further location. These lower couplings can be released using respective operating handles 36, 38, and the whole backrest can be tilted about the lower couplings by operating a rotatable adjusting knob 40 to manipulate a tilt adjusting mechanism (most of which is not seen in Fig. 1) and which causes movement of the backrest relative to the upper couplings 28, 30 to change the angle of tilt of a main body 31 of the backrest relative to the uprights 24, 26. Details of these devices will be described with reference to subsequent drawings. It will be seen from a comparison of Figs. 1 and 2 that all of the controls for the backrest are behind the backrest and that a cover 42 is provided with suitable zippers 44 to allow removal of the cover for cleaning and for adjustment of some of the parts, as will be described. A convenient strap in the form of a loop 46 simplifies handling the backrest when it is to be removed or installed. Reference is next made to Fig. 3 in which the general parts already introduced can be seen in more detail. The main body 31 is molded of a stiff plastics material (preferably polyurethane) having sufficient strength to maintain its shape as well as to support the various devices to be attached to it. The forward face is covered in a resilient padding material 48 as is conventional in this type of structure. The upper couplings 28, 30 include hangers such as hanger 50 shown in Fig. 1. There will be a corresponding hanger on the upright 26 and these hangers will be described in more detail with reference to Figs. 4 and 5. It will also be seen in Fig. 1 that a projection 52 rests in the hanger, and by comparison with Fig. 3, will be seen that a similar projection 54 is associated with the coupling 30. These projections are in alignment one with the other about a common axis and in general terms they are attached to the main body 31. More specifically, they are extensions from a crank indicated generally by the numeral 56. This crank consists of a centre portion 58 terminating at generally parallel offset legs 60, 62 which are connected to respective bearing portions 64, 66 journaled in supporting bearings 68, 70. In turn, the portions 64, 66 end in angled legs 72, 74 which extend generally upwardly and forwardly to meet the projections 52, 54. In turn, these projections end in locating arms 76, 78. Returning to the centre portion 58 of the crank, a frame 80 is pivotally coupled to the portion 58 at sleeve bearings 81, 83 and is in effect a link made out of rods and shaped to provide stability. The frame 80 is also connected by a third sleeve bearing 82 to an actuator 84 which includes the adjusting knob 40. The actuator is anchored in a journal bearing 86 to the main body 31 of the backrest. As will be explained, rotation of the knob 40 results in moving the frame 80 and hence turning the crank 56 thereby changing the orientation of the angled legs 72, 74 and tilting the main body 31 in the wheelchair. Details of how this mechanism operates will be given with reference to Figs. 7 and 8. The lower couplings 32, 34 will now be described. These couplings are similar to one another and the coupling 32 will be described primarily with reference to Fig. 4. This figure is a sectional view on line 4-4 of Fig. 3 and shows a bracket 88 attached by suitable fasteners 90 to the main body 31. The fasteners are arranged in slots 92 to provide some adjustment and the bracket 88 carries a pair of aligned tubular bearings 94 containing a locking bolt 96 and also attached to the bracket is a locating element 98. The bolt 96 and element 98 combine to locate about upright 24 and this is achieved by providing a curved portion 99 at the outer end of the element 98 to complement the curvature of the upright 24, and by providing the bolt 96 with an angled end portion 100 which combines with the curved portion 99 to locate the coupling about the upright 24 when the bolt is in the engaged position shown in Fig. 6. This location is however relatively loose to permit angular movement between the coupling and the upright as the main body is tilted as will be explained. It will also be seen in Fig. 4 that between the bearings 94, a compression spring 102 biases the bolt into this position by virtue of engagement with a transverse pin 104 engaged in the bolt proper. This pin also is located between the element 98 and the bracket 88 to orientate the bolt 96. As seen in ghost outline, the bolt can be withdrawn and then rotated to put the pin against the end of the locating element 98 to hold the bolt in the withdrawn position. To engage the bolt, it is simply rotated and the spring 102 will then move it back to the position shown in full outline in Fig. 6. The lower coupling 34 is of course similar in structure to the lower coupling 32 with the parts reversed so that the engagement against the upright 26 will work in the same way as described with reference to the upright 24 shown in Fig. 6. Reference is next made to Fig. 5 to describe the upper coupling 28 which is typical also of the coupling 30 on the other side of the backrest. The coupling consists essentially of the hanger 50 supporting projection 52 which is shown in ghost outline. In general terms, this projection is attached to the back of the backrest, but in the preferred embodiment it is an extension of the tilting mechanism as previously described. It will be evident that a simplified embodiment could be provided in which this projection 52 is a simple attachment to the backrest and there would then be no tilting adjustment. As seen in Figs. 5 and 6, the hanger consists of first and second parts 106, 108 held together by a clamping screw 110 set in the part 106 and threaded into the part 108 to provide a clamping force. The parts 106, 108 include respective curved arms 112, 114 shaped to fit about the upright 24 while squeezing a thin liner 116 to increase frictional characteristics and to better lock the hanger 50 in position vertically on the polished upright 24. Both of the parts 106, 108 extend from the respective curved arms 112, 114 towards respective raised surfaces 118, 120 which define curved walls 122, 124 shaped to receive the projection 52 with the projection resting on the parts 106, 108 between the upright 24 and the curved walls 122, 124. The projection 52 is secured positively in the position shown in Fig. 5 by a rotatable keeper 126 mounted about a vertical axis defined by a specially formed bolt 128 which has a cylindrical shaft 130 ending at a step and attached to a smaller diameter threaded end piece 132 which permits the bolt to be engaged tightly in the keeper 126. The second part 108 defines a cylindrical recess 134 to receive a compression spring 136 about the cylindrical main shaft 130 to bias the second part 108 towards the keeper 126 in engagement with a low friction washer 138. The result is that the keeper can be rotated about the axis of the bolt 128 and it can also move axially against the bias of the spring 136. Returning to Fig. 5, it will be seen that the keeper is generally L-shaped and that one leg of the L-shape defines a downwardly facing curved recess 140. With the keeper engaged, the projection 52 fits in recess 140 to prevent separation vertically between the projection and the hanger 50. To release the keeper, it is simply rotated using sufficient force to dislodge it vertically so that it will pass over the projection 52. This vertical movement is permitted by the spring 136 shown in Fig. 6 and is illustrated in ghost outline in Fig. 6. To return the keeper, it is rotated in the opposite direction, displacement will again take place, and the spring will cause the keeper to again lock in the position shown in full outline in Fig. 5. It will be evident that the hanger 50 can be attached to the uprights 24, 26 as required to define the vertical position of the backrest. Also, the projections 52, 54 (Fig. 3) are free to rotate in the hangers and this movement permits the tilt mechanism to operate in a manner to be described with reference to Figs. 7 and 8. It will be evident at this point that the backrest can be placed between the uprights 24, 26 after first drawing the bolts 36, 38 to the retracted position to disable the lower couplings 32, 34, and rotating the respective keepers 126 on the upper couplings 28, 30 into disengaged positions. The backrest is then placed between the hangers with the projections 52, 54 engaged in the hangers, and the fixed locating elements 98 in the lower couplings 32, 34 are brought up against the respective uprights. Next the bolts 96 are released so that they will engage the uprights and lock the lower couplings in place. The assembly is completed by rotating the respective keepers 126 (Fig. 5) to lock the upper couplings 28, 30 to the uprights. With this assembly in place, the main body 31 can then be tilted using the mechanism as will now be described with reference to Figs. 7 and 8. A comparison of Figs. 7 and 8 will show that the backrest is in a tilted position in Fig. 7 and a more upright position in Fig. 8. As seen in Fig. 7, the actuator 84 is extended to push the link 80 upwardly thereby causing the crank 56 to rotate about the bearing 68 in the direction of the arrows. As a result, the angled leg 72 will rotate about the projection 52 (Fig. 3) contained in the hanger 50 and this will cause the backrest to tilt clockwise as drawn in Fig. 7 rotating about the lower coupling 32. It should be noted that this coupling is sufficiently loose that it will accommodate tilting and that some vertical movement will take place as the main body tilts. Turning now to Fig. 8, the actuator 84 has been shortened from the Fig. 7 position by rotating the knob 40 to draw the link 80 downwards thereby rotating the crank 56 in a clockwise direction as drawn. This thrusts the backrest forwardly again pivoting about the lower coupling 32. To accommodate this, the crank rotates within the hanger 50 and any necessary vertical motion takes place at the lower coupling 32 as previously mentioned. It will of course be appreciated that this description has been limited to one side of the backrest and a similar motion takes place at the other side. Reference is next made to Figs. 3 and 9 which illustrate a pair of side supports 150, 152 which are adjustable to bring the side supports into contact with the user's lower torso to improve lateral support in the wheelchair. As seen in Fig. 9, the support 152 is essentially aligned with the remainder of the main body 31 of the backrest whereas support 150 has been moved (for the purposes of illustration) into a fully engaged position providing maximum side support. This position is reflected in Fig. 10 which is a sectional view on line 10-10 of Fig. 9. The parts of the side support 150 will be described with reference to Fig. 10 and these parts can be seen also in some detail in Fig. 3. The side support 150 consists essentially of a support piece 154 mounted about a pivot 156 attached to the main body 31 and pivotally connected to a curved rod 158 which is engaged in a locking device 160. The curved rod 158 passes through a base plate 162 mounted on a fixed pin 164 which also carries a pivoted lever 166. The plate 162 and lever 166 are biased away from one another by a compression coil spring 168 with the result that the opening in the lever 166 through which the curved rod passes becomes misaligned about the rod causing frictional forces to lock the rod 158 in position. To release the rod, the lever 166 is moved into the position indicated in ghost outline to compress the spring and align the opening thereby permitting the rod to move freely so that user is able to move the support piece 154 into a desired position before again releasing the lever. The side support 150 is exemplary also of the side support 152. The side supports 150, 152 can be adjusted from behind the backrest by moving the levers 166, adjusting the support pieces 154 as required, and then releasing the levers. For completeness, the assembly is shown in Fig. 11 corresponding to the position of the side support 152 in Fig. 9. Here it will be seen that the structure is collapsed into alignment with the remainder of the main body 31 of the backrest. Such movement changes the position of the lever 166 but it remains available for operation in the manner described. It will also be appreciated that because these structures are accommodated in recesses in the main body 31, they can be concealed by the cover 42 as shown in Fig. 1. Access is by lowering zippers 44. Of course if preferred, the cover could be made to expose the adjusting levers for the side supports. The preferred embodiment of the invention may be modified within the scope of the invention. For instance it is envisaged that in some applications where the uprights will permit it, the upper and lower couplings could be reversed with minor modifications to the structure. The couplings can therefore be referred to as first and second couplings rather than upper and lower to include such a variation. Other variations are within the ambit of the invention as described and claimed. INDUSTRIAL APPLICABILITY Backrests according to the invention will provide support on wheelchairs and permit ready removal and adjustment so that the backrests are particularly useful on collapsible wheelchairs. This is because the adjustability does not hamper to simple arrangement for removal and reattachment. INDEX OF REFERENCE SIGNS 20 Backrest 22 Wheelchair 24 Upright 26 Upright 28 Upper coupling 30 Upper coupling 31 Main body 32 Lower coupling 34 Lower coupling 36 Handle 38 Handle 40 Knob 42 Cover 44 Zippers 46 Loop 48 Padding material 50 Hanger 52 Projection 54 Projection 56 Crank 58 Centre portion 60 Leg 62 Leg 64 Bearing portion 66 Bearing portion 68 Bearing 70 Bearing 70 Bearing 72 Leg 74 Leg 76 Arm 78 Arm 80 Frame 81 Frame 82 Bearing 83 Bearing 84 Actuator 86 Bearing 88 Bracket 90 Fasteners 92 Slots 94 Bearing 96 Bolt 98 Locating element 99 Curved portion 100 End portion 102 Spring 104 Pin 106 First part 108 Second part 110 Clamping screw 112 Arm 114 Arm 116 Liner 118 Raised surface 120 Raised surface 122 Curved wall 124 Curved wall 126 Keeper 128 Bolt 130 Shaft 132 End piece 134 Cylindrical recess 136 Spring 138 Washer 140 Recess 150 Side support 152 Side support 154 Support piece 156 Pivot 158 Curved rod 160 Locking device 162 Base plate 164 Fixed pin 166 Lever 168 Coil spring

Claims: CLAIMS: 1. A backrest (20) for use on a wheelchair (22) having a pair of spaced uprights (24,26) behind the seat, the backrest comprising: a main body (31) shaped to support a user's back and having generally vertical sides; a pair of first couplings (28, 30) attached one to each side of the main body and including a pair of hangers (50) attachable one to each of the uprights at substantially the same heights on the uprights, the couplings further including projections (52) attached to the main body and engageable on respective ones of the hangers in front of the associated uprights to thereby support the backrest vertically and to prevent rearward movement of the backrest as the user leans on the backrest; and a pair of second couplings (32, 34) spaced vertically from the first couplings and one to each side of the main body and extending outwardly away from one another, each of the second couplings including a fixed forward locating element (98) for engagement against the front of one of the uprights to also prevent rearward movement of the backrest as the user leans on the backrest, and a bolt (96) for releasably engaging the rear of the upright to prevent forward movement until released to permit removal of the backrest from the wheelchair. 2. A backrest as claimed in claim 1 in which the hangers further include releasable keepers (126) engageable on the respective projections to prevent upward movement of the backrest relative to the wheelchair. 3. A backrest as claimed in claims 1 in which the projections lie on a common axis and in which the backrest further includes a tilt adjusting mechanism (56, 80, 84) coupled to the main body and to the projections to adjust the relative positions of the projections and the main body thereby tilting the backrest about the second couplings relative to the wheelchair, the second couplings being free to slide on the respective uprights as required during tilting. 4. A backrest as claimed in claim 1 in which the bolts are generally in alignment with one another and biased away from one another. 5. A backrest as claimed in claim 4 in which the second couplings further include a pair of operating handles (36, 38) projecting from the back of the main body and forming parts of the respective bolts for engaging and releasing the bolts. 6. A backrest as claimed in claim 1 in which the hangers are made to be attached to the respective uprights at a selected height on the uprights. 7. A backrest as claimed in claim 3 in which the projections are circular in cross-section and in which the tilt adjusting mechanism includes a crank (56) attached to the projections and an actuator (84) operable to load the crank and thereby rotate the projections and change the tilt of the backrest. 8. A removable backrest as claimed in Claim 1 and further including a pair of side supports (150, 152) adjustably mounted on the main body for movement angularly towards and away from one another. 9. A backrest for use on a wheelchair (22) having a pair of spaced uprights (24, 26) behind the seat, the backrest comprising: a main body (31) shaped to support a user's back and having generally vertical sides; a pair of first couplings (28, 30) attached to the main body and including a pair of aligned projections (52) extending about a common axis, one to each of the vertical sides of the main body, and a pair of hangers (50) for attachment to the uprights to support the backrest; a pair of second couplings (32, 34) spaced vertically from the first coupling and engageable with the uprights to locate the backrest to prevent movement forwardly or rearwardly; and a tilt mechanism (56, 80,84) coupled to the main body and to the projections and operable to move the projections relative to the main body to thereby tilt the main body about the second couplings and relative to the uprights. 10. A backrest as claimed in claim 9 in which the hangers further include releasable keepers (126) engageable on the respective projections to prevent upward movement of the backrest relative to the wheelchair. 11. A backrest as claimed in claim 9 in which the projections are circular in cross-section and in which the tilt adjusting mechanism includes a crank (56) attached to the projections and an actuator (84) operable to load the crank and thereby rotate the projections and change the tilt of the backrest. 12. A backrest as claimed in claim 9 and further including a pair of side supports (150, 152) adjustably mounted on the main body for movement angularly towards and away from one another. 13. A backrest (20) for use on a collapsible wheelchair (22) of the type having a pair of uprights (24, 26) behind the seat, the backrest comprising: a main body (31); a pair of upper couplings (28, 30) including hangers (50) for attachment one to each of the uprights, structure (52) attached to the main body for resting on the hangers, and keepers (126) coupled to the hangers and operable to lock said structure to the hangers; and lower couplings (32, 34) attached to the main body and releasably engageable loosely about the uprights to further locate the backrest on the uprights. 14. A backrest as claimed in claim 13 and further including a tilt adjusting mechanism (56, 80, 84) attached to the main body and operable to manipulate said structure thereby changing the location of the backrest relative to the upper couplings and sliding the lower couplings on the uprights. 15. A backrest as claimed in claim 13 and further including a pair of side supports (150, 152) adjustably mounted on the main body for movement angularly towards and away from one another.

Inventors: HARRISON PATRICK N, JENSEN FINN HOJ, MEDJEDOVIC NENAD B, HARRISON, PATRICK, N., JENSEN, FINN, HOJ, MEDJEDOVIC, NENAD, B.
Applicants: HARRISON PATRICK N, JENSEN FINN HOJ, MEDJEDOVIC NENAD B, SPECIAL HEALTH SYS LTD, HARRISON, PATRICK, N., JENSEN, FINN, HOJ, MEDJEDOVIC, NENAD, B., SPECIAL HEALTH SYSTEMS LTD.
Application year: 1994
Main classification: A61G5
IPC codes: A61G5